塔西南古近系卡拉塔尔组岩相特征与沉积环境

LITHOFACIES AND DEPOSITIONAL ENVIRONMENTS OF THE KALATAER FORMATION,PALEOGENE,SOUTHWEST TARIM BASIN

塔西南地区南天山山前和昆仑山山前广泛出露的古近系卡拉塔尔组为新一轮海进的标志。较干旱炎热气候背景下的碳酸盐岩沉积与古河流携带陆源碎屑的注入共同作用的结果形成了包括介壳灰岩、生屑灰岩、鲕粒灰岩等碳酸盐岩,钙质—粉砂质泥岩、钙质砂岩和石膏岩在内各种岩石类型,并在不同沉积环境形成了不同的岩石组合,构建了从陆相冲积扇到海相浅海陆棚的一个完整的沉积体系。该区可划分为冲积扇至浅海陆棚环境的碎屑岩和缓坡至陆棚的碳酸盐岩两种不同的沉积区域,它们之间的相互作用使得卡拉塔尔组形成了复杂的混合沉积现象,其中以间断混合和相混合为主,同时见有源区混合和原地混合类型。控制这些混合过程的主要因素为构造作用、海平面变化和风暴等突发性事件,气候条件和物源区亦可视为频繁影响因素,水动力因素的控制作用则影响较弱。

The Paleogene Kalataer Formation widely outcrops at the front of South Tianshan Mountain and Kunlun Montain,Southwest Tarim.The deposition of the Kalataer Formation marks a transgression.Carbonate sedimentation in arid climate conditions and siliciclastic influx from ancient rivers led to a range of lithofaces including carbonates（such as shell limestones,bioclastic limestons and oolitic limestones）,argillaceous rocks（such as calcareous mudstones and silty mudstones）,siliciclastic rocks（such as calcareous sandstones and calcareous siltstones）and evaporites.Rock assemblages with different composition in different regions reflect a depositional system ranging from alluvial fan to neritic shelf,which can be divided into two main depositional facies：1）siliciclastic depositional facies from alluvial fan to neritic shelf,and 2）carbonate depositional facies from ramp to shelf.The interaction of these two facies led to a mixture of siliciclastic-carbonate sediments.The controlling factors are tectonic activities,sea level change,and storm events,paleoclimates,and source areas;hydrodynamic conditions seems to have exerted a limited control on the mixing of carbonate and siliciclastic sediments.